1. Field of the Invention
The present invention relates to a pulse oxymeter having a probe which is adapted to be set on a body surface of a subject.
2. Discussion of the Prior Art
There is known a pulse oxymeter for measuring a blood oxygen saturation of a subject, including a probe which supports (a) a first device for emitting toward a body portion of the subject a first light having a first wavelength and a second light having a second wavelength different from the first wavelength, and (b) a second device for detecting an intensity of each of the first and second lights transmitted through, or reflected by, the body portion of the subject and generating a photoelectric pulse wave signal representative of the detected intensity of each of the first and second lights. The pulse oxymeter further includes (c) a third device for determining a blood oxygen saturation of the subject based on the pulse wave signals corresponding to the first and second lights. The probe of the pulse oxymeter is set on a body surface of the subject where a blood oxygen saturation is measured with respect to the blood flowing through the underlying peripheral blood vessels including capillaries.
In the event, however, that a patient is subjected to stress or invasion during a surgical operation, the peripheral blood vessels of the patient may constrict and consequently the blood flow through the peripheral blood vessels may be reduced to an insufficient amount, or lost in an extreme situation. In such events, the pulse oxymeter is not capable of obtaining an appropriate photoelectric pulse wave signal since the amount of the blood flow through the peripheral blood vessels is insufficient, and accordingly the pulse oxymeter is not capable of providing blood oxygen saturation readings in a reliable and precise manner, or carrying out the measurement itself of blood oxygen saturation.